Dynamic S-palmitoylation of proteins controls a variety of key signaling pathways in eukaryotes that are not well understood. Our laboratory has recently developed robust chemical tools to rapidly analyze dynamic S-palmitoylation of proteins and identify S-palmitoylated proteins on large-scale. The grant application describes that application of our chemical tools to fission yeast in order to dissect the mechanisms that regulated S-palmitoylation. Our preliminary studies have revealed defects in S-palmitoylation that influence whether fission yeast cells divide (mitosis) or differentiate (meiosis). These preliminary data are very exciting as it begins to identify molecular mechanisms that eukaryotic cells use to control decision-making and cell fate and highlights the utility of Sz. pombe for mechanistic studies in S-palmitoylation. The detailed analysis of dynamic S-palmitoylation proposed in this grant is therefore essential for understanding the basic mechanisms of cell signaling and is important for dissecting the defects in protein S-palmitoylation associated with human diseases such as cancer and neurological disorders.